Comparison between deformation modulus of national concretes made with coarse aggregates from different mineralogical origins

ABSTRACT

Knowing the concrete properties is crucial for a safe and efficient design, mainly in a scenario marked by the adoption of increasingly slender elements and increasingly large spans. When not experimentally determined, the static deformation modules of national concretes are estimated by the equations contained in ABNT NBR 6118. In 2014, such equations underwent significant changes. New coefficients were inserted and, in addition to the characteristic resistance to compression of the composite, the nature of the coarse aggregate came to be considered. However, it is worth discussing how representative the equations used and the coefficients attributed to each type of rock have been in practice. Added to this is the fact that the concrete deformation modules are influenced by numerous factors, the compressive strength of the material being only one of them. Starting from a set of experimental results, this work evaluated how the values of the initial tangent deformation modulus of concrete (Eci) have behaved with different coarse aggregates, from different regions in the country. The influence of the parameters water/cement (W/C) ratio, slump, density also have been investigated, as well as the affinity of the results obtained with the current 2014 version of NBR 6118, with some of its previous versions, and foreign codes were also investigated. As results, the two models obtained to estimate Eci as a function of the W/Cratio, slump, density and concrete compressive strength at 28 days showed precision between 70% and 90%. Among the properties addressed, the density (ρ) was the one that most influenced the Eci values. The other models obtained were more conservative than the normative models for concretes containing limestone. For granite/gneiss aggregates all the models were equivalent. For basalt, the normative models were more conservative than those found here.

Keywords
Concrete; Mechanical properties; Deformation Modulus; Coarse aggregate